The field of electrosurgery includes a number of loosely related surgical techniques which have in common the application of electrical energy to modify the structure or integrity of patient tissue. Electrosurgical procedures usually operate through the application of very high frequency currents to cut or ablate tissue structures, where the operation can be monopolar or bipolar. Monopolar techniques rely on a separate electrode for the return of RF current that is placed away from the surgical site on the body of the patient, and where the surgical device defines only a single electrode pole that provides the surgical effect. Bipolar devices comprise both electrodes for the application of current between their surfaces.
Electrosurgical procedures and techniques are particularly advantageous since they generally reduce patient bleeding and trauma associated with cutting operations. Additionally, electrosurgical ablation procedures, where tissue surfaces and volume may be reshaped, cannot be duplicated through other treatment modalities.
Generally, radiofrequency (RF) energy is used during arthroscopic procedures because it provides efficient tissue resection and coagulation and relatively easy access to the target tissues through a portal or cannula. However, a typical phenomenon associated with the use of RF during these procedures is that the currents used to induce the surgical effect can result in heating of fluid in the area. While some minimal heating of the fluid may occur as the fluid flows over an active electrode of an energy based device, this fluid is typically effectively removed via evacuation of the fluid through tubing or aspiration elements associated with the device or disposed adjacent the device. However if the flow of fluid is disrupted or reduced, possibly due to a clog, the fluid may be exposed to the electrical current delivered to the electrode for longer periods of time, thereby increasing fluid temperatures. This heated fluid could potentially transfer high temperatures through the fluid transport walls of the tube or transport element to other portions of the device adjacent the tube, such as mechanical and electrical components, potentially damaging the device. In addition heated fluid may transfer high temperatures through suction tubing walls extending from the device, the suction tubing potentially laying across and coming into contact with the patient or surgeon along its path and potentially causing patient or surgeon burns.
Fluid flow may be inadequate or disrupted, elevating fluid temperatures for a variety of reasons. For example, the surgeon may be pushing the device up against tissue, preventing adequate fluid flow volume through an aspiration aperture. Alternatively the flow system may have been set at an insufficient setting or pressure for the energy setting of the energy delivery system. This reduced volume of fluid may more readily warm and therefore increase the overall temperature of the fluid aspirated. As a further example, debris may sometimes partially clog the aspiration aperture or aspiration lumen, again reducing the flow. This hotter fluid may then increase the temperature of the device and particularly the outer wall of the aspiration tubing walls, potentially causing instrument failure or injury to the patient or attending medical staff. Of note however, should the fluid flow system become completed clogged, eliminating most of the flow, the temperature may drop. This over-temperature system and method disclosed here does not expressly detect a complete clog of the system. An improved system and method to sense, limit and actively reduce the temperature of the fluid being drawn through the device and thereby the temperature of the tubing is desired.